diff --git a/libaegisub/common/hotkey.cpp b/libaegisub/common/hotkey.cpp
index c0be25f8b..a2cebeef9 100644
--- a/libaegisub/common/hotkey.cpp
+++ b/libaegisub/common/hotkey.cpp
@@ -15,6 +15,7 @@
 #include "libaegisub/hotkey.h"
 
 #include "libaegisub/cajun/writer.h"
+#include "libaegisub/fs.h"
 #include "libaegisub/io.h"
 #include "libaegisub/json.h"
 #include "libaegisub/log.h"
@@ -43,6 +44,7 @@ struct hotkey_visitor : json::ConstVisitor {
 	std::string const& context;
 	std::string const& command;
 	Hotkey::HotkeyMap& map;
+	bool needs_backup = false;
 
 	hotkey_visitor(std::string const& context, std::string const& command, Hotkey::HotkeyMap& map)
 	: context(context), command(command), map(map) { }
@@ -72,6 +74,7 @@ struct hotkey_visitor : json::ConstVisitor {
 		key_str += static_cast<std::string const&>(key_it->second);
 
 		map.insert(make_pair(command, Combo(context, command, std::move(key_str))));
+		needs_backup = true;
 	}
 
 	void Visit(const json::Array& array) override { }
@@ -100,6 +103,7 @@ void Hotkey::BuildHotkey(std::string const& context, json::Object const& hotkeys
 		hotkey_visitor visitor{context, command.first, cmd_map};
 		for (auto const& hotkey : command_hotkeys)
 			hotkey.Accept(visitor);
+		backup_config_file |= visitor.needs_backup;
 	}
 }
 
@@ -183,6 +187,9 @@ void Hotkey::Flush() {
 		combo_array.push_back(keys);
 	}
 
+	if (backup_config_file && fs::FileExists(config_file) && !fs::FileExists(config_file.string() + ".3_1"))
+		fs::Copy(config_file, config_file.string() + ".3_1");
+
 	io::Save file(config_file);
 	JsonWriter::Write(root, file.Get());
 }
diff --git a/libaegisub/include/libaegisub/hotkey.h b/libaegisub/include/libaegisub/hotkey.h
index 7d866f6b3..81cae91fb 100644
--- a/libaegisub/include/libaegisub/hotkey.h
+++ b/libaegisub/include/libaegisub/hotkey.h
@@ -67,6 +67,7 @@ private:
 	HotkeyMap cmd_map;                  ///< Command name -> Combo
 	std::vector<const Combo *> str_map; ///< Sorted by string representation
 	const agi::fs::path config_file;    ///< Default user config location.
+	bool backup_config_file = false;
 
 	/// Build hotkey map.
 	/// @param context Context being parsed.
diff --git a/tests/tests/hotkey.cpp b/tests/tests/hotkey.cpp
index f81f99206..de0dc9d08 100644
--- a/tests/tests/hotkey.cpp
+++ b/tests/tests/hotkey.cpp
@@ -17,6 +17,8 @@
 #include <libaegisub/fs.h>
 #include <libaegisub/hotkey.h>
 
+#include <fstream>
+
 using namespace agi::hotkey;
 
 static const char simple_valid[] = R"raw({
@@ -196,3 +198,22 @@ TEST(lagi_hotkey, combo_stuff) {
 	EXPECT_STREQ("cmd2", c.CmdName().c_str());
 	EXPECT_STREQ("Default", c.Context().c_str());
 }
+
+TEST(lagi_hotkey,  old_format_is_backed_up_before_migrating) {
+	{
+		std::ofstream tmp("data/hotkey_tmp");
+		tmp.write(simple_valid, sizeof(simple_valid));
+	}
+
+	{
+		Hotkey h("data/hotkey_tmp", "{}");
+		h.SetHotkeyMap(h.GetHotkeyMap());
+	}
+	{
+		std::ifstream tmp("data/hotkey_tmp.3_1");
+		ASSERT_TRUE(tmp.good());
+		char buff[sizeof(simple_valid)];
+		tmp.read(buff, sizeof(buff));
+		ASSERT_TRUE(memcmp(buff, simple_valid, sizeof(buff)) == 0);
+	}
+}